The present invention pertains to rotary or dual action buffing, polishing and finishing pads and, more particularly, to a composite system that includes an intermediate cushioning layer having a graded compression load deflection (CLD) and a thin performance layer that provides the necessary surface finishing function, but can be easily and inexpensively replaced when worn or damaged. The graded compression load deflection fixture performs and replaces the function provided by full thickness prior art buffing pads. The system of the present invention provides a consistent compression load deflection over the useful life of a wide range of buffing materials and avoids the problems of pad degradation and operator fatigue associated with prior art systems. In a particularly unique embodiment, the performance layer is attached to a cushioning layer having a rounded outer edge that permits finishing operations in a full range of angles up to 90°.
The current state of prior art systems typically includes a backing plate with minimal cushioning in combination with a monolithic full thickness polymeric foam buffing pad. Polymeric foam buffing pads have been used for many years to perform a variety of buffing and finishing functions for painted and clear coat surfaces in the automotive and other industries. The full thickness pad provides a combination of surface finishing performance and cushioning effect required for proper operator performance. However, open cell polyurethane foam materials are expensive. Typical polyurethane foam pads range in size from less than 6 inches to greater than 8 inches (about 150-200 mm) in diameter, and 1.25 to 1.75 inches (about 30-45 mm) in thickness. The thickness of the material, in particular, is necessary to provide proper cushioning for the desired finishing operation. However, only a small part of the surface contacting face of the pad is actively used for the desired buffing or finishing operation. The use of full thickness pads thus results in about ⅔ of the pad being unnecessarily wasted when the thin operative surface contacting face is exhausted by wear, damage or contamination.
Notwithstanding the accepted performance of open cell polyurethane foams in buffing, polishing and finishing operations, the high cost of these materials is not the only drawback. All polymeric foams undergo some amount of permanent collapse and decrease in thickness after an applied load. The open cellular structure of these materials is crushed under load and the initial thickness is never fully recovered. In addition, different grades of open cell polyurethane foam have varying compressibilities and, as a result, perform differently in a finishing operation. In addition, open cell polyurethane foams are typically hydrophilic and will absorb water in use. The result is that the compressive strength and cushioning effect of full thickness foam pads is greatly diminished with repeated use. Heat generated in use also increases softening. As a result, with a full thickness open cell polyurethane buffing layer, most of the cushioning effect is lost and performance rapidly degrades with use. Finally, although polyurethane foam pads with curved outer edges have been developed, permitting the operator to buff on an angle, great care must still be taken by the operator to avoid edge load concentration because of pad edge configuration or a lack of cushioned support which can result in cutting or burning of the painted surface. The cushioned rounded edge of one embodiment of the system of the present invention solves these problems.
Other buffing pad materials, such as tufted wool, are also typically provided with a long nap (i.e. 1.25 inches or more) that provide a significant cushioning effect while the actual buffing performance is carried only by the outer ends of the wool strands. In these products, the ingress of water and finishing compound into the base of the fibers which are tufted to a backing layer, results in fiber loss and rapid deterioration in cushioning performance.